Electrode.



J. T. H. DEMPSTER.

ELECTRODE. APPLICATION FILEDJULY 20, 19054 RENEWED AERJG, 1910.

976,990, APPLIUATION FILEDDEC.9.1912. 29,

Witnassesi v Inventor:

W John THDempster,

UNITED STATES PATENT OFFICE;

JOHN T: H. DEMPSTER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPGRATION. OF NEW YORK.

ELECTRODE.

Specification of Letters Patent.

. REISSUED Patented. Nov. 29, 1910.

Application filed July 20, 1905, Serial N 0. 270,470. Renewed April 6, 1910. Serial No. 553,842.

To all whom it may concern:

Be it known that I, JOHN T. H. DEMPSTER, acitizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electrodes, of which the following is a specification.

My present invention relates to electrodes and more particularly to electrodes which give what are known as flaming or luminous arcs. An advantageous method of forming such electrodes has been found to'consist in placing the electrode material proper in a metallic tube or shell. In assembling such electrodes the following methods have fre- The electrode material has been placed in the tube or shell in the form of a powder or it has been molded into pencils and the pencils inserted in the tube or shell. When the electrode material is inserted in the tube in the form of a powder, a certain amount of compression is necessary in order to render the electrode compact and homogeneous. Owing to the physical characteristics of the electrode material ordinarily employed if a shell say 6 to 12 inches in length is first filled with the powdered'material and an attemptis then made to compress the material into the tube, difliculty is experienced from the fact that the powdered material does not flow readily. To obviate this difficulty the tubes while being gradually filled with powdered materialhave been agitated in order that the powdered material may pack under the action of gravity. With this method, however, the density of the powdered material at the lower end of the tube is usually greater than the density of the powdered material at the upper end of the tube. I have found that these difficulties may be obviated if the tube is filled with the powdered material in stages or sections, and after each stage or section is filled the material in the tube be compressed by some external means such as the plunger of a suitable press. \Vith this method of operation .and the pressure usually employed an cilimolded in a press, after which it is baked to drive off the moisture. The baking operation cements the particles to ether, probably by reason of a slight oxidation or from other cause. As the conditions require that the pencils should fit tightly in the inclosing tubes or shells difficulty is sometimes experienced in inserting the pencils in the cases, particularly as slight deformations of the pencils are frequently produced in the baking operation. Some difiiculty is also experienced in obtaining a molded pencil of uniform density from the same or similar causes as those which render it difficult to obtain a. uniform density of dry powdered material in an inclosing shell or case as above set forth. These difficulties, however, are less marked with the molded pencils than with the electrode first described.

I have found that excellent results are obtained by forming the molded filling for the tube or casing in short sections and inserting sections one at a time in the tube or casing. this method the irregularities in form or density of the pencils produced are much smaller than with molded pencils of greater length, The features of my invention hereinbefore set forth are of more or less general utility. I have obtalned excellent results, however, in employing the invention in connection with the electrodes formed essentially of oxygen compounds of iron, titanium and chromium. In particular I have employed it. in conjunction with electrodes formed of approximately 70 parts of magnetite and 30 parts of rutile to which is added from 121} to 15 percent. by weight of chromite. I

With an electrode containing different materials such for instance as an electrode having the composition above described, I have found that the composition of the electrode some times changes with its consumption. In other words, in the consumption of the electrode various constituents contained in a given portion of the electrode as originally formed are not consumed in the same period. As a result the composition of the arcing portion of the electrode may vary sometimes continuously and according of the electrode by slightly varying the com-- position of the different sections forfning one electrode, putting in the sections more remote from the arcing end of the elec trode more of the constituents which are the more rapidly consumed and less of the constituents which are more slowly consumed For in--- than in the sections less remote. stance, I have sometimes found it advisable to decrease the refractory chromite content of an electrode of the composition above described in the sections remote from the arcing end of the electrode.

\Vith electrodes having a composition substantially as set forth above, difficulties are occasionally experienced from a pit or crater formation in the arcing end of the electrode when the electrode is initially started. If for any reason a minute crater or -pit is formed at the arcing end of the electrode when initially started, there is a tendency for the pit or crater to automatically increase in depth and maintain itself for a considerable period of time. I have found, however, that this trouble may be almost entirely avoided if the entire arcing end of the electrode be treated with a small amount of material which is more easily fusible than the body of the electrode. The advantage from the use of this easily fusible material I think is probably due to the fact that it tends to make the arcing end of the electrode uniformly and easily fusible. It also insures a fat are when the electrode is initially put into operation.

When the electrode is treated as above described, the are wanders slowly over the entire arcing surface of the electrode without the formation of a crater at any point. After the electrode has been put in service and the are has played over its entire arcing surface difficulty isseldom experienced in subsequently starting a satisfactory are from the electrode.

The various features of novelty which characterize my invention are pointed out with articularity in the claims annexed to and orming a part of this specification. For a better understanding of my invention, however, reference may be had to the accompanying drawing and descriptive matter in which I have illustrated and described somewhat in detail forms in which my invention may be' ':mbodicd.

()f the drawings, Figure l is an elevation of an electrodecomprisinga mvtal tube and a filling in the fornro't' molded pencils of. a short. length; Fig. 2 is a section of the electrode shown in Fig. 1; Fig. 3? isa sectional elevation of an electrode comprising J l l 1 end of the tube 1 is closed by is a perspective view of the metal disk inclosin the arcing end of the tube; Fig. 6 is a similar view of the paper wad or ca saturated with a fusible salt; and Fig. 5 1s a perspective view of one of the short .pencils.

Referring to the drawings; 1 represents a metal tube or casing which may be formed outof a strip of sheet iron the edges of which are united in a lap seam 2. The lower a disk which may be formed of any suitable material. such as wood and is retained in place by crimping over on it the lower end of the tube 1. The tube 1 has inserted in it many suitable manner, as by means of a. plunger of a press suitable for the purpose, a number of molded pencils or sections 3, 4, 5, 3, 7 and 8, which may be made in any suitable manner. At the upper end of the upper pencil or section '3 is placed a disk'of any suitable absorbent material such as paper, which has been saturated with some easily fusible material such as )otassium titinate or carbonate. Over the isk 9'is placed a thin disk formed of.,metal such as iron '10. The upper end of the tube '1 is crimped over the edges of the disk 10 to secure it in place. 'lhescctions,l3, 4, 5, 6, 7-and 8, may in many cases be identical in form and composition. When it is desired to graduate the-compositioirof the electrode to compensate for its consumption as by placing in some of the sections more chromite than in others the sections may differ slightly in composition from each other. For instance, sections 3, 4, 5, (i and 7 may each contain more chromite than sections 4, 5, 6, 7 andS, respectively.

' The construction shown in Fig. 3 differs from that shown in Figs. 1 and 2 in that the sections 3, 4', l", 6', 7 and 8 are formed of powdered material, the section last enumerated being inserted first and compressed and the other sections successively thereafter. The sections 3, 4, 5, 6', 7"and 8 may be identical in composition or may vary in the manner described above with refcrence to the sections 3, t, 5, (3, 7 and 8.

\Vhile l have described the best forms of my invention now hnown to me, it. will be obvious to those skilled in the art that. changes may bepnade in the form of the in rcntion disclosl'd without; departing from the spirit; thereof, and that. M'l'lillll features of my invention may be employed with-advantage in some cases without. the corresponding use of other features of' my inrcntion.

l'Vhat- I claim as new and desire to secure I by Letters lateut; of the United States, is,----

I. An elect rode consistin of a casin and substantially uniform density.

2. An electrode consisting of ac'asmg and a metal tube and pmvdered filling; Fig. 4 a filling therefor in successive sections of- -a filling therefor in successive sections of is capable of giving a luminous are.

5. An electrode, the body portion of which is compounded of refractory mate rials of different degrees of refractoriness,

the percentage of the more refractory constituents increasing toward the arcing end of the electrode. a

6. An electrode, the body portion of Which is made of a compound of magnetite, rutile and chromite, the percentage of chrotalic OXlClS and having at its arcing end an the electrode.

7. An electrode formed essentially of me tallic oXids and having at its arcing end an easily fusible compound.

8. An electrode formed essentially of metallic oxides and having at its arcing end a fusible salt.

9. An electrode formed essentially of metallic oxids and having at its arcing end a quantity of potassium carbonate;

10. An electrode comprising a body por tion of metallic compounds, at the arcing end of Which is placed a mass of absorbent.

material saturated with an easily fusible compound.

11. An electrode comprising a tube, a filling therefor, an absorbent mass treated with a solution of vaporizable compound placed at one end of said filling, a retaining member covering said absorbent mass, and held in place by the crimping over of the end of the tube or casing. v

12. An electrode at one end of which is placed an amount of absorbent material saturated With an easily fusible compound.

13. An electrode comprising a body .portion of a given composition, and a starting material of different composition placed at the arcing end of the electrode.

Inwitness whereof, I have hereunto set my hand this 18th day of July, 1905.

JOHN T. H. DEMPSTER. Witnesses BENJAMIN B. HULL, MARGARET ELWOOLLEY. 

